--- menu_icons.module
+++ (clipboard)
@@ -237,6 +237,7 @@
  */
 function menu_icons_css_generate() {
 
+  global $base_url;
   $css = "";
   $result = db_query("SELECT mlid, options FROM {menu_links}");
   $pos = variable_get('menu_icons_position', 'left');
@@ -260,7 +261,7 @@
 
       // Retrieve the image dimensions
       $info = image_get_info($image_path);
-      $image_url = base_path() . $image_path;
+      $image_url = str_replace($base_url, '', file_create_url($image_path));
 
       // Support private filesystem
       $css .= theme('menu_icons_css_item', array('mlid' => $item->mlid, 'path' => $image_url, 'size' => $info['width'], 'pos' => $pos));